Measurements of Higher Order Effects in QCD from the Tevatron Collider

Quantum Chromodynamics has been studied extensively at Fermilab's Tevatron collider. Between 1992 and 1996 the D{\O}and CDF experiments, each accumulated approximately $100 \mathrm{pb}^{-1}$ of proton-antiproton collisions at a center-of-mass energy $\sqrt{s}=1800 \mathrm{GeV}$ and $\sim 0.5 \mathrm{pb}^{-1}$ at $\sqrt{s}=630 \mathrm{GeV}$. In this paper, we present selected recent measurements of higher order effects in QCD: multiple jet production and subjet and charged particle multiplicities in quark and gluon jets.Comment: 4 pages, 3 figures in epsi file, talk given at XXXI International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong China. URL http://ismd31.ccnu.edu.cn

Inclusive jet cross-sections and dijet azimuthal decorrelations with D0

We present a preliminary measurement of the inclusive jet cross-sections based on an integrated luminosity of 378 pb^{-1} acquired with the D0 detector between 2002 and 2004 at a center of mass energy of \sqrt{s}=1.96 TeV and a measurement of azimuthal dijet decorrelations based on an integrated luminosity of 150 pb^{-1}. The cross section measurements are based on an iterative cone algorithm with a cone size of R=0.7. They are performed in two rapidity bins between 0.0 and 0.8. The measurements are in good agreement with next to leading order calculations. The azimuthal angle between the two leading jets is sensitive to higher order QCD effects. The measurement of dijet azimuthal decorrelations therefore probes these effects without explicitly reconstructing more than two jets. Except for large azimuthal angles where soft effects are important the measurements are well described by the next to leading order perturbation theory.Comment: Presented at HEP2005 International Europhysics Conference on High Energy Physics, July 21st - 27th 2005, Lisboa, Portugal (4 pages, 5 figures

Agricultural resources investigations in northern Italy and southern France (Agreste project). Part 1: Activity performed on the Italian test-sites

The author has identified the following significant results. Some qualitative results were obtained out of the experiment of reflectance measurements under greenhouse conditions. An effort was made to correlate phenological stages, production, and radiometric measurements. It was found that the first order effect of exposure variability to sun irradiation is responsible for different rice productivity classes. Effects of rice variety and fertilization become second order, because they are completely masked by the first order effects

Gravitational Effects in g Factor Measurements and High-Precision Spectroscopy: Limits of Einstein's Equivalence Principle

We study the interplay of general relativity, the equivalence principle, and high-precision experiments involving atomic transitions and g factor measurements. In particular, we derive a generalized Dirac Hamiltonian, which describes both the gravitational coupling for weak fields, as well as the electromagnetic coupling, e.g., to a central Coulomb field. An approximate form of this Hamiltonian is used to derive the leading gravitational corrections to transition frequencies and g factors. The position-dependence of atomic transitions is shown to be compatible with the equivalence principle, up to a very good approximation. The compatibility of g factor measurements requires a deeper, subtle analysis, in order to eventually restore the compliance of g factor measurements with the equivalence principle. Finally, we analyze small, but important limitations of Einstein's equivalence principle due to quantum effects, within high-precision experiments. We also study the relation of these effects to a conceivable gravitationally induced collapse of a quantum mechanical wave function (Penrose conjecture), and space-time noncommutativity, and find that the competing effects should not preclude the measurability of the higher-order gravitational corrections. Surprisingly large higher-order gravitational effects are obtained for transitions in diatomic molecules.Comment: 19 pages; RevTeX; some typographical errors correcte

Magnetoresistance studies of La2/3Sr1/3MnO3La_{2/3} Sr_{1/3} MnO_3 - YBa2Cu3O7YBa_2 Cu_3 O_7 - La2/3Sr1/3MnO3La_{2/3} Sr_{1/3} Mn O_3 trilayers with ferromagnetic coupling along the nodal direction of YBa2Cu3O7YBa_2 Cu_3 O_7

I have successfully prepared (110) trilayers of \LSMO-\YBCO-\LSMO. Magnetization measurements on these samples reveal a stronger coupling between the ferromagnetic layers. The coupling is an order of magnitude higher than that seen in the case of (001) trilayers. Magnetoresistance measurements show a first order transition in the data coinciding with the antiferromagnetic regime deduced from the magnetization measurements. I have also measured the anisotropic magnetoresistance (AMR) of these samples revealing an unusually high AMR ($\sim 72000$). I attribute such a high AMR to the pair breaking effects in these films.Comment: 12 pages, 7 figure

Three photon absorption in ZnO and ZnS crystals

We report a systematic investigation of both three-photon absorption (3PA)spectra and wavelength dispersions of Kerr-type nonlinear refraction in wide-gap semiconductors. The Z-scan measurements are recorded for both ZnO and ZnS with femtosecond laser pulses. While the wavelength dispersions of the Kerr nonlinearity are in agreement with a two-band model, the wavelength dependences of the 3PA are found to be given by (3Ephoton/Eg-1)5/2(3Ephoton/Eg)-9. We also evaluate higher-order nonlinear optical effects including the fifth-order instantaneous nonlinear refraction associated with virtual three-photon transitions, and effectively seventh-order nonlinear processes induced by three-photon-excited free charge carriers. These higher-order nonlinear effects are insignificant with laser excitation irradiances up to 40 GW/cm2. Both pump-probe measurements and three-photon figures of merits demonstrate that ZnO and ZnS should be a promising candidate for optical switching applications at telecommunication wavelengths.Comment: 13 pages, 7 figure

Influence of ionospheric perturbations in GPS time and frequency transfer

The stability of GPS time and frequency transfer is limited by the fact that GPS signals travel through the ionosphere. In high precision geodetic time transfer (i.e. based on precise modeling of code and carrier phase GPS data), the so-called ionosphere-free combination of the code and carrier phase measurements made on the two frequencies is used to remove the first-order ionospheric effect. In this paper, we investigate the impact of residual second- and third-order ionospheric effects on geodetic time transfer solutions i.e. remote atomic clock comparisons based on GPS measurements, using the ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The impact of third-order ionospheric effects was shown to be negligible, while for second-order effects, the tests performed on different time links and at different epochs show a small impact of the order of some picoseconds, on a quiet day, and up to more than 10 picoseconds in case of high ionospheric activity. The geomagnetic storm of the 30th October 2003 is used to illustrate how space weather products are relevant to understand perturbations in geodetic time and frequency transfer.Comment: 25 pages, 10 eps figures, 1 table, accepted in Journal of Advances in Space Research, Special Issue "Recent advances in space weather monitoring, modelling and forecasting

Third-Harmonic and intermodulation distortion in bulk acoustic-wave resonators

This article discusses on the measured third-order intermodulation (IMD3) products and third harmonics (H3) appearing in a set of six different solidly mounted resonators (SMR) and bulk acoustic-wave (BAW) resonators with different shapes and stack configurations. The discussion is supported by a comprehensive nonlinear distributed circuit model that considers the nonlinear effects potentially occurring in any layer of the resonator stack. The aluminum-nitride (AlN) and silicon-dioxide (SiO2) layers are identified as the most significant contributors to the IMD3 and H3. The frequency profile of the third-order spurious signals also reveals that, in temperature-compensated resonators, where the SiO2 layers are usually thicker, the remixing effects from the second-order nonlinear terms are the major contributors to the IMD3 and H3. These second-order terms are those that explain the second-harmonic (H2) generation, whose measurements are also reported in this article. Unique values of the nonlinear material constants can explain all the measurements despite the resonators have different shapes, resonance frequencies, and stack configurations.Peer ReviewedPostprint (author's final draft

The Lyman α forest as a tool for disentangling non-Gaussianities

© 2014 IOP Publishing Ltd and Sissa Medialab srl . Detection of primordial non-Gaussianity will give us an unprecedented detail of the physics of inflation. As observational probes are now exploring new expanses of the inflationary landscape, it is crucial to distinguish and disentangle effects of various non-Gaussianities beyond f NL . In this work, we calculate the effects of non-Gaussianities parametrized by f NL and the cubic-order g NL , on the Lyman α-forest flux measurements. We give the expressions of the bias due to f NL and g NL , which can be deduced from accurate measurements of the transmitted flux. We show how these two effects can be cleanly disentangled via a flux transformation, which also keeps the error in check